Since its introduction as an '86 1/2 model the flagship of Toyota, the Supra, has received a varied reaction from enthusiasts. On the one hand, the inline 6-cylinder, 3.0-liter with 4-valves per cylinder offers as smooth and fluid a transition of power as this writer has ever driven and reflects a welcome improvement from the earlier 2-valve, 2.8-liter unit. On the other, in naturally aspirated trim the 200-horsepower and 185-ft/lbs of torque do nothing to mask the increased weight of the new chassis.
The '87 model brought power hungry Toyota buyers a new choice in the form of the intercooled turbocharged model. With 230-hp and 245-ft/lbs torque the new Supra Turbo rewards the driver with enough power to motivate it more than 3500 lb mass to consistent 7.0 sec 0-60 runs and low 15 second passes in the mid 90's through the quarter mile. With our stock '88 test model we witnessed a best time of 6.89 in the -60 proving it close to a second quicker than our tests of the stock Nissan 300ZX Turbo.
Subjectively, acceleration aside, the biggest improvement we witnessed in playing with both versions of the car was the massive increase in mid-range torque. This torque adds flexibility to highway driving and means dropping down a gear is just not required in most maneuvers, except those beyond the limits of prudent social/moral behavior. Unfortunately those of us without the pressures of a conscience still find the performance envelope to be less than hoped for on the world's first inline six, 4-valve per cylinder, intercooled turbo engine. (NOTE: we have found with the Supra, they take several thousand miles to get broken-in and we have noted differences in zero-to-sixty times of several tenths of a second between a stock Supra with less than two thousand miles and one with 15,000 miles on it).
In terms of chassis, the stock Supra is equipped with what can only be referred to as, "THE RIGHT STUFF" with the only unequal length A-Arm suspension from Japan. To set the record straight, there as few production vehicles that can lay claim to this state of the art race car chassis technology, those coming to mind are, Porsche's 928 S-4 and some of the new Mercedes line. Again though, the state of tune in the chassis is more refined than ready and eager. For a more detailed look at the base Turbo Supra, see the January 1987 issue of TURBO.
In both the engine and the chassis, the excellent foundation found in the base Supra Turbo makes upgrading the performance both reasonable and a relatively easy task. As far as engine performance goes five manufacturers, Borla, Cartech, HKS, and Spearco, Turbo Accessories (Going) and TRD (Toyota Racing Development) offer a variety of components to enhance engine performance. The most reasonable first step being a low restriction exhaust system as independent testing has shown that the back pressure from the standard system is approximately equal to boost pressure at about 5800 rpm under full load.
EXHAUSTING STUDY
The stock exhaust has three basic points of restriction, first on the turbine discharge tube there is a pre-catalyst, second at a bolted flange placed in the area of the clutch bell housing there is the main converter and at the rear of the car a massive muffler. Before modifying our car we sought out and found baseline back-pressure info from tests conducted during the development stage of one of the aforementioned manufacturers.
The tests showed that at stock boost pressures of 6.8 psi, the total system restriction is 6 psi. The restriction brakes down to 3 psi in the front of both converters together and surprisingly, a like amount is found in front of the muffler. This means that for a change, a smog legal version using the muffling properties of the pre and main converters coupled to an ultra low restriction muffler can allow for impressive gains in both response and overall horsepower. Our hat is off to Toyota's cat, which several aftermarket manufacturers have noted is one of the best found on a Japanese car to date.
Looking at the eight different exhaust systems from four different manufacturers can be complicated, but with the help of Pacific Coast Performance in Santa Ana, California and their 500-horse Clayton chassis dyno we were able to get some power readings on some of the systems.
BORLA makes two different systems, both of T304 stainless steel construction featuring a lifetime warranty. Both Borla systems employ 2.5" diameter mandrel bent tubes and a single 2.5" inlet, dual 2" outlet drilled core muffler. Borla has been using the drilled core technology the longest of the various competitors. Cartech and HKS both use similar mufflers and say they do so to allow for the greatest available flow area within the limited space. Looking at Borla's two systems, the first starts after the cat and the other, as tested, includes a new head pipe without the pre-cat, as well as a main cat by-pass. Our initial testing on the unit was performed with the main cat in place and showed a 30-horse gain at the rear wheels at 5000 rpm with no other modifications. In later testing, with the Cartech intercooler, on both the dyno and at the drag strip we enjoyed a slight improvement with a cat by-pass in place.
CARTECH makes the widest variety of exhaust systems with four. Included are bold mild stainless steel systems and both are available in legal (after the converter) and "off-highway" (turbo outlet to rear bumper systems). Like the Borla and the HKS versions, all Cartech systems bolt together in the stock locations and employ stock hangers and are built using 2.5" diameter mandrel tubes. Cartech’s mild steel versions use two side by side steel packs at the rear of the car, while their T-304 units use a Borla muffler, utilizing a 2.5" inlet size with two 2.25" pathways and outlets. It should be noted that the Cartech version had slightly longer outlet pipes in back of the muffler which would prevent any discoloration if a body kit such as the Kaminari unit shown is employed. The T-304 stainless, using the Borla Muffler and 2.5 inch tubing system was tested with both converters in place (horsepower for the Cartech unit was not tested independent of other modifications).
HKS manufactures one system which is a fully aluminized 2.5" competition system starting right at the turbo going to a straight-through muffler in the position of the factory main converter and continuing back to an HKS single 2.5" inlet by dual 2" outlet aluminized muffler. The HKS system can be installed with or without (for racing use only) the cat. Our chassis testing has shown that bolting on the competition systems (no cat) from the various manufacturers averages a 35+ horsepower increase to the rear wheels at 5000 rpm with no other modifications. The HKS system proved this out with a dyno verified 36 total rear wheel horsepower increase in our tests.
SPEARCO PERFORMANCE PRODUCTS markets one system, an aluminized unit which starts at the back flange of the cat and uses 2.5" mandrel bent tubing joining to a low-restriction Walker Super Turbo muffler which shows a marked reduction in back pressure from the factory system. The Spearco unit is the only system using the reverse flow muffler technology and is also the only system exiting the car with just one chrome outlet.
It should be noted with the horsepower gains on all of the tested exhaust systems that the boost pressure did increase slightly, about 1 to 2 psi due to the lower backpressure. This also allowed the turbo to spool-up faster. Our conclusion: if your performance budget is limited and you are only going to be able to make one modification to your Supra, a performance exhaust system should be the first item on your list, and with eight different systems from four different vendors Supra owners have a very good choice of product and pricing levels.
INCREASED BOOST
There are several devices available to turn up the boost on a Turbo Supra, ranging from Spearco's simple bleed-off set-up using a "T" fitting and a hose, to different manual boost control valves including the HKS (Electronic Valve Controller) and Cartech's newly updated QCBC (Quick Change Boost Control). The factory has built in a fuel cut circuit which shuts things down at between 11.4 and 13.7 psi boost, depending on load and volume of air through the air mass sensor. So unless you are planning on getting real serious and defeating this device, stay under 11 psi.
HKS offers two boost control systems, a conventional dial-a-boost and their new "EVC". A complete description of this unit will be found elsewhere in this issue, so we won't go into detail here except to say that it is slick.
CARTECH offers another choice in electronic boost control units, the new second generation QCBC along with a version of the venerable old dial-a-boost. For the Supra the QCBC includes a modified factory cruise control switch that mounts in the change pocket on the left side of the steeling wheel. The QCBC gives the driver a choice of stock, or a pre-set high boost pressure and defaults back to stock every time you turn off the ignition, keeping parking lot attendants from going into hyperspace with your new Supra. A mere touch of the switch by the knowing owner flips you back to warp drive, which on the test car from Cartech was set at 14 psi. We have to give Cartech some credit to responding to our criticisms, as the new QCBC shows a marked improvement in control from earlier units and functioned as well as the EVC, although without quite the flexibility.
SPEARCO offers a simple bleed system which is set at 14 psi with the FCBC and works quite well for its price, making the choice in boost control units almost as broad as exhaust systems, and again with a large variation in price depending on how sophisticated you want to go.
TRD uses their own pre-load system on the wastegate itself, which not only holds the wastegate closed longer to obtain the desired boost pressure, but by applying this additional pressure holds the wastegate firmly closed, allowing a slightly faster time to boost.
Taking the boost up a couple psi from the stock 6.8 psi would be a good second step for a Supra project.
HIGH BOOST PRESSURES
If you want to go for the gold, and can figure out the acronyms, there are two devices on the market which will allow you to by-pass (or move up) the Toyota factory fuel cut point, allowing you to exceed the fuel cut point; HKS offers a FCD (Fuel Cut Defencer) and Going (Turbo Accessories) builds the FCBC (Fuel Cut By-pass Circuit), both of which increase the factory fuel cut off point.
Here a word of warning must be inserted. In doing some of the research for this article we received some conflicting, but important information. In talking to HKS, TRD, Turbo Accessories and Cartech, it was unanimous that while adding a fuel cut device would allow the car to exceed the factory fuel cut point, operation at those pressures without fuel enrichment and reductions in temperatures could lead to detonation and engine damage. Depending on who we talked to, the word extended had different meanings, but the bottom line was that it will cost SERIOUS BUCKS to replace the engine. Our recommendation is that if you are going up past the factory fuel cut point; add fuel enrichment for lower thermal stress.
Conflicting somewhat with the above statements, our chassis dyno testing of Turbo Magazine's own project car showed 8% to 9% CO up to 12 psi and no signs of detonation. This car, however, is equipped with a larger Cartech intercooler. Conversely we have had quite a few reports of detonation at pressures as low as 12 psi. Again to be safe, a good recommendation would be to add a fuel enrichment device when going to boost pressures over 11 psi.
HKS's method of fuel enrichment is the "PFC F-CON" which is a "piggy-back" type computer that plugs into the car's computer and lengthens the signal to the injectors under the boost. This unit has a fuel curve programmed into it to work with the Supra, but also includes a manual dip switch, allowing some fine tuning.
CARTECH offers a secondary fuel pump and fuel pressure regulator which starts adding in additional fuel pressure on an appropriate curve after a pre-set boost point. While this attacks the problem from a different angle, it works well, as even when running at 14 psi the car was still showing 9% CO with no sign of detonation on the dyno.
GOING incorporates a circuit into the FCBC that holds the injectors open longer (close to 98% of the duty cycle) at boost pressure exceeding that of the factory fuel cut. In some of our testing we found that while the system worked well on the street/track, it put out almost too much fuel under maximum load on the dyno, making it almost a failsafe to 14.7 psi.
INTERCOOLER UPGRADES
The factory intercooler leaves little to be desired with regards to both pressure drop and cooling effectiveness. When we ran our first dyno tests on the Supra (TURBO Jan '87) we thought the restriction at higher boost pressures was actually in the turbo, but in conferring with Cartech, Spearco and HKS it was found that the stock intercooler itself was a major contributor to the problem. Testing at Cartech showed the stock intercooler to have a 3 psi pressure drop at 6.8 psi and a whopping 4.3 psi pressure drop at 9 psi. In other words, the turbo had to do the same work and therefore, produce heat as if it was run at 13.3 pounds of boost, while the engine itself was only seeing 9 pounds of boost.
All of these intercoolers are similar in size except that the Spearco unit also employs slightly larger diameter tubing in some locations going to and from the intercooler.
The only intercooler we were able do to an actual before and after test with on our own car were one of the units from Cartech. At stock boost pressure we found an 11-horsepower gain between the stock and Cartech intercooler. While this gain was actually measured at the stock (8 psi w/exhaust) boost pressure, it should be noted that intercooler efficiencies are best tested in a real world or street environment with actual air flow across the core. Previous testing on the Cartech intercooler showed a 7/10 psi drop at 6.8 psi and 1.10 psi at 14 psi which basically agreed with our dyno runs. In addition to actual pressure drop, Cartech testing of the intercooler showed 89% efficiency vs. 68% on the factory unit. With the similarity in intercooler upgrades, it would be safe to say that any one of these would be an almost mandatory option if you are starting to go for serious boost.
TURBO UPGRADE
Already a popular item in the Japanese performance aftermarket, turbo upgrades for the Supra are just now becoming available here in the US.
We have tested the HKS turbo kit for non-turbo Supras which uses a Garrett T04B, and while this car is a little on the lazy side below 3000 rpm, when the bigger turbo gets in full motion at about 3600 rpm, it hits like a sledge hammer. In fact, during our dyno testing one of these combinations put out 320-hp to the rear wheels at 5500 rpm. Cartech is now doing a compressor upgrade on the Toyota turbo, using a new compressor wheel and machining out the compressor housing. At the present time these units are being sold on an exchange basis only, but a pattern for new compressor housing is underway and may be available by the time this article reaches you.
In driving a car equipped with the Cartech upgrade, it is noticeably stronger on the top-end than a comparable car with the stock turbo, but does not suffer the low-end loss of the T-4. During our quarter mile testing the Cartech car with the compressor upgrade was running about 5 mph faster through the quarter than the exact same car without the compressor upgrade. The strange thing was that the car with the Cartech compressor upgrade was actually running almost a mile per hour faster than the HKS car with the T-4. This was also verified by the dyno which showed it putting out 330 horsepower to the rear wheels @ 5000 rpm... this is serious horsepower.
BOOST FOR NON-TURBO SUPRAS
HKS offers their Turbocharger kits in three different stages ranging in boost pressures from 4.3 psi up to 12.0 psi. "Stage 1" is a non-intercooled system featuring HKS "PFC F-CON" electronic fuel management system, the "Twin Power" and "EGC" electronic ignition system, a cast iron exhaust manifold that allows the bolt up of a Garrett T04 turbo with a water cooled bearing section and a remote racing type HKS wastegate, a compressor by-pass valve and an HKS boost gauge. "Stage II" allows boost to be raised a couple of psi and includes a 3mm head gasket, as well as a full exhaust system.
The big gun from HKS is their "Stage III" system which includes a new set of injectors and a different prom for the "F-CON" in the "Stage I," a large intercooler and plumbing, a heavy duty clutch pressure plate and disk, an oil cooler and a "VBC" (non-electric) variable boost control. We tested one of their "Stage III" "killer kits" for about a week, including some strip time, and as mentioned earlier, it is strong. Using the large Garrett T-4 turbo with a lowering of the naturally aspirated car's compression ratio by use of the thick head gasket, doesn't give quite the low-end of the smaller Toyota unit, but mid-range and top-end get quite serious. Dyno testing showed a maximum of 320-horse to the real wheels at 5500 rpm and quarter mile speeds were in the 106.88 mph range running at 13 psi.
Cartech offers a complete intercooled system for the Supra 3.0, as well as for the '82 Supra 2.8. The Cartech system for the 3.0 features the Cartech fuel pressure regulator and high-output Bosch pump, an Autotronic Controls, MSD and Turbo Timing Master electronic ignition system, a cast iron exhaust manifold to which a T04 with water cooled bearing and a Rajay remote racing wastegate, a massive 26" x 12" x 3" air to air intercooler, a compressor by-pass valve, a K&N low restriction air filter and a VDO boost gauge. This allows the capability to safely run 9 psi of boost. Although Cartech's fuel system is good to 11 psi on 92 octane they suggest the conservative 9 psi setting. They, however, do offer properly prepared engines with ported heads and forged pistons if a higher level of operation is desired. In dyno tests independent of ours at Texas Turbo the Cartech system has produced bhp to over 300 at 8 psi.
HANDLING IMPROVEMENTS
During our testing we were able to try out several suspension combinations on different vehicles, in addition to the one we had prepared at TRD. For our project, TRD recommended and installed the same system proven on the track by their cars in the Escort series, which facilitates changing the shocks and springs while retaining the stock bars. The new high-performance gas shocks from TRD are designed to work with the factory TEMS system, and in fact the installation came with a switch mounted in place of the change box, that allows you to set the TEMS to the full firm mode at all times. Normally the TEMS computer, which monitors steering angle, brake system hydraulic pressure, road speed and throttle position will not go to full firm unless certain circumstances require it. TRD utilizes sport springs with both a 40% higher rate and a two-inch drop. Although the overall ride became very stiff, stiffer than perhaps a casual enthusiast might enjoy, the overall handling characteristics were vastly improved. In addition, a superior "on center" and "straight line" stability feel was present. The only problem we encountered was that of light scraping of the aero kit on some steep driveways.
The Cartech suspension package used specially would springs manufactured for them by Suspension Techniques that dropped the car 1 1/4-inch with a 12% higher rate which seemed to eliminate the scraping in some of the same situations.
The Cartech system utilized to manually adjust Tokico shocks which during our testing were set to the firm mode. We had some split emotions between the one and two inch drop springs, with the older staff members favoring the one inch and the younger favoring the slightly stiffer two-inch. Here personal preference enters in.
In addition to this package, Suspension Techniques also manufactures a wide variety of suspension components for import and domestic vehicles including their own Supra package with 28 mm front and 24 mm rear anti-sway bars working in conjunction with front springs that deliver a 25% increase in rate, and rear springs that increase the spring rate 27% over stock. The S/T suspension system lower the Supra about 1 1/2" from a stock counterpart. S/T has long been a suspension supplier for serious performance enthusiasts.
AERODYNAMICS
Two companies offer complete aero kits for the Supra, Kaminari and A.S. Auto Mechanical (D.P. Motorsport). Both our red project car and the white Cartech factory turbo used the Kaminari kits, while the burgundy Cartech car with the full turbo kit used the D.P. Motorsport unit. Both are quality units, constructed of hand laid fiberglass, and unlike a lot of the copy-cat body kits, each enjoys their own unique styling. Some of our staff liked the Euro-look side effect of the D.P. while everyone liked the rear of the Kaminari. The Kaminari seemed to be slightly thicker fiberglass than the D.P. and fir better than any kit we have seen recently. Taking advantage of Kaminari's color matching program we received a front spoiler, side skirts and a rear lower skirt painted to a fantastic match. Next we found that the panels supplied replaces the factory bumper covers front and rear and bolt-on at the factory locations, this made for a tight and tidy installation that has no hint of being anything short of factory quality.
The change in the car's overall esthetic appearance with the aero-kit is really dramatic and the silver BBS 3-piece wheels contrast the red car in a way that can only be described as fantastic. In addition, these wheels helped trim some pounds off our slightly overweight sport roof version of the Supra. As can happen with a two-inch lowering, we did have to watch some driveways at speed, but that is part of the game. We noticed the white car with only a one-inch drop had less problems with steep driveways.
WHERE THE RUBBER MEETS THE ROAD
To test out some of the different performance combinations we went first to Carlsbad Drag Strip near San Diego, California. Before getting into the speed and ETs, you have to remember one thing about the wonderful suspension of the Supra... it was not designed for drag racing. All of the cars showed excessive "wheel hop" if a hard launch was attempted, so the cars were basically driving off the line at a point slightly above "bogging" before getting the pedal down. We had some serious tires on some of these cars, including 245 Goodyear Z rated "S" compound, Yokohama AVS, and Bridgestone RE-71s, all tires known to be sticky, but once the boost went up on launch, excessive wheel spin and accompanying hop were incurred, so the major number we were looking at was the speed, which reflected the horsepower, vs. the ET which basically in this case was a test of launching. Now with the excuses out of the way...
The Turbo Magazine project car featuring Borla exhaust, Cartech intercooler, HKS EVC, Going FCBC, TRD's shocks and springs, a set of Bridgestone RE-71 tires on BBS 3-piece alloy rims and a Kaminari aero package ran a best of 103.25 miles per hour, with ET's in the low 14 seconds, with a best of 14.36. This car dyno tested at a constant maximum of 295-horsepower.
The Cartech project car featured Cartech’s own stainless exhaust with both cats in place, FCBC, upgraded intercooler, QCBC, and the Cartech compressor upgrade. This car also featured Cartech suspension and Goodyear 245-45/225-50 "Z" rated "S" compound tires ran a best of 13.54 at 107.14 and interestingly enough on one run, ran up against a stock GNX being tested by Turbo City and driven by Tom "Mongoose" McEwen. While the "Mongoose" did not waste any time leaving the line and as well ahead of Cartech's Todd Gartshore, who got a fair launch and "reeled him in," passing him well before the lights and surprising a lot of people. This car dyno tested out at a whopping 330-horsepower.
This HKS project car was a non-turbo fitted with their Stage III turbo kit as listed above, stock suspension, Hayashi 3-piece wheels and Yokohama AVS 245-45 rear/225-50 front tires. As mentioned earlier, this car was equipped with a T-4 turbo and launching took some practice to keep from either bogging or full-out wheel spin/hop. It ran a best speed of 106.88 with ET's in the high 14's, best of 14.64. This car dyno tested out to a maximum of 320 horsepower, showing the correspondence between speed and horsepower between this and the Cartech car.
The fourth car, an HKS upgraded factory turbo car with an intercooler upgrade, EVC, FCD, PFC F-CON, and exhaust system was equipped with stock wheels and Toyo 600 C1 225-50 tires. This car tested at LACR (Palmdale, CA) the following week and ran a best of 104.43 (corrected), and a best of 14.41 before frying the clutch. This car was dyno tested at 260 rear wheel ponies at 10 psi of boost. We were unfortunately unable to obtain a higher setting than 10 psi on the dyno due to loading problems, however, calculating from what our other test vehicles had done at similar boost pressures and verifying this with miles per hour figures at the strip, we can safely say that the actual power at 13 psi to the rear wheels would be a minimum of 285 and a maximum of 295 hp.
CONCLUSION
On the surface, the supple line of the Supra and adult appeal of the car full of the newest in technology may not strike fear into the hearts of Corvette, Mustang GT, Grand National or other mavens of big inch engine lore, but with the help of the goods outlined herein - it should. As mentioned, due to the independent rear suspension, the Supra was not designed to be a drag strip car, but a full-fledged luxury grand touring vehicle, which it accomplishes well. The fact that one of our test cars ran in the mid-13's at 107.14 and then went on to be radar clocked at a top speed of 157 miles per hour in the exact same trim a few days later is, however, a testament that a properly prepared Supra is a car to be reckoned with in any situation.
